Characteristics of aerosols over Beijing and Kanpur derived from the AERONET dataset

Özet

Beijing and Kanpur are two cities identified as high aerosol optical thickness (AOT) and complexcomposition of aerosols in Asian monsoon regions. Detail knowledge of key aerosol types in these twocountries would be helpful for clarifying the mechanisms of aerosol radiative forcing and improving theaccuracy of satellite remote sensing in these two countries. This study examines the characteristics ofaerosol types over Beijing and Kanpur derived from a 12-year dataset from Aerosol Robotic Network(AERONET) stations and compares them via cluster analysis of optical and microphysical properties.Aerosols in Beijing are more complex than in Kanpur. Four fine-size dominated aerosol types (includingtwo types of moderately absorbing aerosols, one highly absorbing aerosol type and one non-absorbingaerosol type) and one coarse-size dominated aerosol type are identified over Beijing. In Kanpur, twofine-sized dominated aerosol types (one high absorbing aerosol type and one non-absorbing aerosoltype) and one coarse-sized dominated aerosol type are obtained. Compared to Beijing, the average SSAsof non-absorbing and high-absorbing aerosols are lower for the four wavelengths (440 nm, 676 nm,869 nm, 1020 nm) in Kanpur. High absorbing aerosols usually occur in the months December to February(DJF) for both sites. The proportion in Kanpur (14%) is about twice that in Beijing (7%). Non-absorbingaerosols are usually observed in the months June to August (JJA) for both sites. Their proportion inKanpur (31%) is ~3 times larger than that in Beijing (11%). Coarse aerosols are frequently observed in themonths March to May (MAM) for both sites. Their proportion in Kanpur (54%) is two times larger than inBeijing (21%).